This patent application claims the benefit of the earlier filed Chinese Patent Application serial number 200910266832.7 filed on Dec. 30, 2009.
This invention relates a low odor aqueous styrenic polymer dispersion comprising acetoacetoxy or acetoacetamide functional polymer particles or acetoacetoxy or acetoacetamide additives and at least one organic amine having high boiling point. The aqueous polymer dispersion is useful for preparing coatings without the unpleasant odor of styrene containing dispersion.
Elimination of odorants from polymer dispersions is long-desired in polymer industry, especially for consumer products with olfaction requirements. The odorants have different chemical nature including residual monomers, impurities in monomers or in other raw materials of the polymerization process. The elimination methods include, heating the polymerization mixture for a prolonged period with or without addition of ion- or free radical-source to raise the monomer conversion ratio, vacuum stripping or steam sparging to physically remove hydrophilic odorants and using enzyme to enzymolysis ester odorants. However, these methods are time consuming and raise the cost of the manufacture processes.
In styrene containing polymer dispersions, it is difficult to remove the unpleasant odor which may be volatilized from the styrenic monomer or other compound(s) in the dispersion that have not been identified. Prolonging the polymerization period, steam stripping for several times or using enzyme can not achieve a satisfactory deodorization of the dispersion.
One effective method for deodorizing polymer dispersions is to add chemicals reacting with residual monomers and generating odorless adducts or converting to a less odorous species such as non-volatile adducts. U.S. Pat. No. 5,616,651 discloses a process to prepare a rubbery polymer, which includes a step to deodorize the polymer emulsion obtained. This deodorizing step is carried out under conditions which allow for an additional aminoalcohol to react with residual monomers n-butylacrylate and acrylonitrile which is presented in the emulsion. However, the deodorizing method is only applied to the residual n-butylacrylate and acrylonitrile. The odor from styrene and/or impurities from the styrene monomer or other raw material in polymerization is still desired to be eliminated.
EP 1,553,106 discloses a low odor polymer dispersion that containing styrene monomer. The deodorants containing aminoalcohol, hydroxylamine and hydrazine are uses to reduce the content of benzaldehyde of the dispersion. However, these deodorants are not applied to deodorizing of residual styrene and/or impurities from the styrene monomer.
U.S. Pat. No. 6,969,734 discloses an aqueous polymer dispersion containing acetoacetoxy functional polymer particles and an alkyl ethoxylated surfactants, which is useful for preparing coatings having improved adhesion to substrates. The acetoacetoxy functional groups are used for the purpose of potential crosslinking of the polymer particles. In a preferable embodiment, in order to minimize hydrolysis of the pendant acetoacetoxy groups, one or more bases are added to the aqueous polymer dispersion to raise the pH to a value in the range of from 8 to 11. Suitable bases include ammonia, or primary amines such as ethanolamine, methyl amine, or isopropyl amine. The invention also discloses that, optionally, the aqueous polymer is treated to remove volatile organic compounds (VOCs) by processes such as steam stripping or distillation. However, the prior art reference does not disclose that the odor of some of the aqueous polymer dispersions comprising styrenic monomers can be eliminated by mixing with two or more of above mentioned compounds such as, for example, the acetoacetoxy functional polymer particles and ethanolamine, and by steam stripping. Neither appropriate amines nor amount of the amine effective for such deodorizing is disclosed.
It is, therefore, an object of this invention to provide styrenic aqueous polymer dispersions free of unpleasant odor, methods for preparing low odor polymer dispersion and low odor coating compositions prepared therefrom.